It is known to provide coin validators which store data defining individual sets of ranges or "windows" the validators being arranged to test items to determine whether they have properties falling within any one of a plurality of sets of windows. If the properties are all found to lie within the windows of a particular set, the validator issues a signal indicating that a valid coin of a particular denomination has been tested.
It is common for such validators to be capable of validating any of a plurality of different denominations of coins. It is often desirable to provide means for preventing the validator from accepting coins of a specific denomination. For this purpose, validators have been provided with individual switches each associated with a respective coin denomination. The switches can be operated to control which denominations are accepted by the validator. The provision of the switches adds to the expense of the validator, occupies valuable space and renders the setting-up of the validator more troublesome in its design. It is also necessary to ensure that the engineer setting-up the validator knows the relationship between the switches and the respective coin denominations.
It is also desirable in some situations to be able to vary the ranges for one or more particular coin denominations. For example, it may be found that genuine coins of a particular denomination tend to get rejected by the validator. To avoid this problem, it may be necessary to widen one or more of the windows in the set associated with that denomination. Alternatively, it may be necessary to narrow one or more of the windows if it is found that counterfeit coins are being erroneously accepted as coins of that denomination. It would be possible to provide further switches to allow for these modifications, but this would further exacerbate the problems mentioned above.
It has been proposed (see British Patent Application No. GB-A-2238152 to store in a validator sets of windows associated with counterfeit coins. If an item is tested and found to have properties lying within the windows of a particular set, then that item is rejected, even if its properties also lie within the windows of a set associated with a genuine coin denomination. These "rejection windows"enable the validator more readily to reject specific types of counterfeit money without significantly preventing acceptance of genuine coins. It would be desirable also to provide a simple means for controlling whether or not the rejection windows are used.